Newbie questions about custom moves

I'm tentatively planning to run my first DW session sometime during the holidays, but am still uncertain about a few things.

When do you inform players about custom moves? Take, for example, the "When you open a sewer hatch..." move on page 347 of the rulebook. Would you tell them about that when they enter the sewers, or when they first attempt to open a hatch?

When creating a custom move, may I assume that the only time I need to worry about coming up with a list of 10+, 7-9, etc. results is if the move would be triggered by a character's deliberate action?

With that out of the way, could you tell me whether the following might be a valid custom move? I'm thinking of running a session based loosely on the old D&D B1 module "In Search of the Unknown," and I thought the Room of Pools would be a good place for one.

When you drink from one of the pools, roll + WIS (not sure if it should be WIS or CON). On a 10+, choose 1. On a 7-9, choose 1, but the water has a secondary effect that the GM will tell you about. On a miss, the GM will tell you what happens.

• Heal 1d6 damage.
• Take +1 ongoing to hack and slash until the next time you make camp.
• See in your mind's eye the location of the nearest treasure.

(These are just placeholders. There may be more/other options.)

Does that work? What if someone else drank from the same pool? (The pools in the original module had different effects, but they weren't random.) Would you need a "When you drink from the same pool..." move?

The moves triggers when they do the thing that triggers it. Otherwise, no need to tell them.

GM principle: Never speak the name of your moves.

I like your move! The secondary effect that the GM will tell the player's about is a great way for you to add a little variety and make the effects of drinking from the pool different for every player (if you like).

Rather than just a mechanical +1, I like giving the players narrative / move options for their imbubing the pool. So I'd have as an option (instead of the +1 to hack and slash)
* Choose a beginning move from a playbook not in play that you may use until you next make camp.

That sort of thing.

Thanks! The original module has an entire room of pools, filled with everything from healing potions to green slime. I thought that "the GM will tell you what happens" leaves the door open for me to be as cruel or benign as the situation warrants. (Though it likely would be less of "you just drank green slime!" and more of "giant tufts of hair emerge from your ears.")

I like your suggestion, but am wondering if that would be the right thing for an introductory game. You're right that +1 is pretty bland; I expect that the final menu of choices would be (hopefully) more imaginative.

My thought about how I would handle a second character drinking from the same pool was this:

When you drink from a pool that one of your colleagues drank from, roll + WIS . On a 10+, you gain the same benefit as your colleague and choose 1 more from the above list; choose 1. On a 7-9, you gain the same benefit as your colleague, but the water has a secondary effect that the GM will tell you about. On a miss, the GM will tell you what happens.

It's cool to present custom moves in a variety of ways.  For example, you could print it out on a card and slide it over to them when they enter the room.  In this case, you're telling them something about the pools and it's kind of a dare or a temptation, right?  Want to really tempt them, just write out the trigger and show them that-don't show them the rest of the move unless they trigger it.   Other times, you could wait till they triggered the move, then show it to them, and then ask if they're still sure that's what they want to do.  Here, showing them the move is like them beginning to do something and then realizing how things could go down and what's at stake.  Other times, moves are about stuff they already know, you're just telling them there's a mechanism for it - for example, if the characters are out in a blizzard and you have a crossing slippery ice move, the characters know what ice is all about and you can put that out at the beginning of the session. 

This situation can be handled in so many different ways.  On the one hand, you could literally just say what your prep demands.  If you drink from pool number one, this happens.  It's just like describing the contents of a room, etc. 

On the other, the pools could have random effects.  That's where a custom move might come in.  It gives an advantage to the wise or the tough to drink from a pool and gives everyone a chance to spin the wheel, so to speak.  It also says something about the pools themselves.

Try to think about how other moves (particularly Spout Lore and Discern Realities) might interface.  If someone Discerns "what here is useful to me" or w/e how will that effect the randomness of the pools?

I remember the Room of Pools! And the strange green gem that might grant a wish if you place a chip of it under your tongue. Hah!

Do you even want to roll? doesn't the module give a list of great descriptions of pools? (This pool is full of hissing, steamy lumps of white rock. What do you do? This pool is full of Green Slime. What do you do?)

Yeah, I don't have anything helpful to say. My first DnD experience was that module. I'm just going to sit here and glow in the memories.